Odin class submarine

The Odin-class submarine (or "O class") was a class of nine submarines developed and built for the Royal Navy in the 1920s. The prototype Oberon was followed by two ships ordered for Australia, and six modified boats ordered for the RN. Three modified ships were built for the Chilean Navy as the Capitan O'Brien-class submarines in 1929.

They were built to replace the aging L-class submarines which did not have adequate endurance in the Pacific. These boats were theoretically able to dive to 500 feet, though none were formally tested beyond 300 feet. Armament consisted of eight 21-inch torpedo tubes (6 bow, 2 stern) and one 4-inch gun. The boats were of a saddle tank type with fuel carried in riveted external tanks. These external tanks proved vulnerable to leaking after depth charge damage betraying the position of the submarine. These boats were the first British submarines fitted with Asdic and VLF radio which could be used at periscope depth.